Terminal blocks are widely used in electrical wire layout operation in automatic control for interconnecting different electrically conductive wires. A prior art terminal block, commercially available in Europe for many years, is shown in FIGS. 1-4, comprises a block-shaped body 1, two fixing screws 2, an elongate pressing bar 3, and two vertically movable clamping members 4. The clamping member 4 is integrally stamped and formed from a T-shaped thin metal strip. The clamping member comprises a top portion having a threaded hole 4A, two lateral sides (4B, 4C) bent downwardly and overlapped at the bottom of the clamping member, and two tabs 4D transversely overlying the overlapped portion of the two sides (4B, 4C) and bent downwardly, perpendicular to the two sides, defining a space 4E allowing the pressing bar 3 to extend therethrough.
The body 1 has at the front surface two longitudinally parallel spacing ribs 1A each defining therein a space 1B allowing the clamping member 4 to move vertically along therein (FIG. 3). A notch 1C is formed at the middle section of the rib 1A at same horizontal position, allowing the pressing bar 3 to pass through. A seat 1D is disposed above each space 1B and has through hole 1E extending through the inner bottom of the seat. The hole 1E is dimensioned to allow the threaded shank 2A of the fixing screw 2 to pass through but stop the enlarged head 2B of the fixing screw 2. The fixing screw 2 may be threaded through the threaded hole 4A (FIG. 2).
The body 1 further has on the left and right sides two guiding apertures 1F, respectively, communicating with the spaces 1B and allowing two electrically conductive wires 5 to insert from the aperture 1F into the clamping member 1B. As shown in FIG. 2, the pressing bar 3 and the two clamping member 4 each may freely move along the space 1B and the notch 1C at one direction and, therefore, before the finished assembled terminal blocks leave where they are manufactured, the two fixing screws 2 need be tightly threaded into the threaded hole 4A of the clamping member 4 to prevent components from loosening and escaping during shipment. In this case, the aperture 1F from which the conductive wire enters into the guiding aperture 1F is blocked by the tab 4D of the clamping member 4, as shown in FIG. 2. It should be noted that when in use, the conductive wire 5 is inserted from the guiding aperture 1F to be in between the pressing bar 3 and the inner bottom of the space 4E of the clamping member 4 and clamped therebetween. Accordingly, to use such a terminal block for wire interconnecting, a user must firstly loosen the fixing screws 2 with a screw driver 6, as seen from FIG. 3, to lower the clamping members 4, insert the wires 5 from the guiding apertures 1F in between the pressing bar 3 and the inner bottm of the space 4E of the clamping members 4, and finally tighten the fixing screws 2 to raise the clamping member 4 so as to firmly holding the wires 6 between the pressing bar and the clamping member.
As can be seen from the above, the user needs to firstly loosen the fixing screws 2 and then tighten them. This is a tedious and time-expending work. Furthermore, the conductive wire 5 is intended to be clamped between the pressing bar 3 and the overlapped sides (4B, 4C) of the clamping member 4, however, as shown in FIG. 4, the overlapped sides (4B, 4C) may not maintain its original shape and is forced to open outwardly, although when the fixing screws are driven by a power-operated or a pneumatic screw driver that often impart excessive axial force to the fixing screws. It is understood that the ribs 1A formed of weak plastic structure cannot resist the force that causes the clamping member 4 to deform. Therefore, the conductive wire 5 may no longer be properly positioned due to the lack of sufficient compression force applied thereon, and pulled off from the terminal block, which causes the risk of short of circuit. Besides, the components of the above described terminal block are expensive to manufacture, particularly the pressing bar 3 which needs conductivity and rigidity sufficient to sustain compression force and thus require material of a greater thickness. The formation work of the clamping member 4 and the tapping work thereon also increases the production cost.